Remove read_expression and use parse_expression directly

app/main.c

@@ -16,13 +16,15 @@ static bool step_repl(void)
 	const int len = read_line(getchar, buffer, BUFFER_SIZE);
 	if (len < 0)
 		return false;
-	const expression_t *e = read_expression(&pool, buffer, len);
-	if (NULL == e) {
+
+	expression_t *expression;
+	const int used = parse_expression(&pool, buffer, len, &expression);
+	if (used != len) {
 		puts("Invalid expression\n");
 		return true;
 	}
 
-	const int result = evaluate(e);
+	const int result = evaluate(expression);
 	printf("%d\n", result);
 
 	return true;